A method of selecting a scanning sequence of a laser beam in a selective laser solidification process, in which one or more objects are formed layer-by-layer by repeatedly depositing a layer of powder on a powder bed and scanning the laser beam over the deposited powder to selectively solidify at least part of the powder layers, includes determining an order in which areas should be scanned by: projecting a debris fallout zone that would be created when solidifying each area based on a gas flow direction of a gas flow passed over the powder bed; determining whether one or more other areas to be solidified fall within the debris fallout zone; and selecting to solidify the one or more other areas that fall within the debris fallout zone before solidifying the area from which the debris fallout zone has been projected.